This invention relates to fiber optics communication systems and, more particularly, to an apparatus and method for improving operation of such systems by reducing extraneous signals therein.
Fiber optics communications systems are in widespread use, and find application for communicating a wide variety of information, including telephone, video, and audio information.
In one type of fiber optics communications, a single light-emitting diode ("LED") is used in a system that both transmits and receives information over a fiber optics link. Typically, the LED is coupled to both a transmitter and a receiver via a solid state switch. In the transmitting mode, a suitable modulated electronic signal is applied to the LED which is forward biased and operates to generate light as a function of the applied electronic signal. In the receiving mode, the LED is reverse biased, and draws a certain amount of leakage current, called "dark current". This leakage current adds to the current that is generated as a result of the detection of received light, and adds a spurious component to the detected signal. The use of a single diode for both the transmitting and receiving functions is advantageous from the standpoint of efficiency, but the exhibited dark current is troublesome.
It is among the objects of the present invention to reduce or eliminate the problem of dark current in the described type of system, or in any system wherein an LED is utilized to receive and detect optical signals.